Multi-linking, rear suspension system for two-wheeled motor vehicles

ABSTRACT

A rear suspension system for two-wheeled motor vehicles having a generally triangular configuration includes upper and lower pivot arm assemblies pivotally connected to a frame of the vehicle. A control arm is interconnected between the pivot arm assemblies. A rear wheel supporting unit, including upper and lower arm assemblies, is connectable to an axle of a rear wheel of the vehicle at a first end thereof. The upper arm assembly of the supporting unit is connected to the upper pivot arm assembly. The lower arm assembly of the supporting unit is connected to the lower pivot arm assembly. A compressible shock unit is provided to dampen movement of the system.

RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 10/414,631, filed Apr. 15, 2003, which is a continuation-in-partapplication of U.S. application Ser. No. 10/050,315, filed Jan. 15,2002, which is a continuation-in-part application of U.S. applicationSer. No. 09/740,517, filed Dec. 19, 2000.

BACKGROUND OF THE INVENTION

The present invention relates generally to two-wheeled vehicles. Moreparticularly, the present invention relates to a rear suspension systemfor two-wheeled motor vehicles, such as motorcycles, employing pivotingarm assemblies and control arms possessing shock absorptioncharacteristics and providing lateral stability.

The existing designs of most prior art rear suspension assemblies fortwo-wheeled motor vehicles include a rear pivot from a single pointeither from a dual or mono shock system that either extends or comprisesthe shock unit. In this respect, when the shock system is affected bypower or braking to the rear wheel, system efficiency and stability arecompromised. Other systems use a quad-type configuration that onlyconnects to a small section of the frame, providing less structuralintegrity.

Although recent motorcycle frames include a swing arm configuration,these configurations posses certain deficiencies that detract from theiroverall utility. The swing arm movement is typically in a singlepivoting motion with no lateral stability. This causes lateralinstability for the rear wheel of the motorcycle. Many existingsuspension systems provide inadequate control of the wheel to pavementcontact. This can create safety concerns regarding the control of theincreased stopping during braking. Aside from the rear wheel wobbling,as described above, many current designs transfer force back to thefront of the vehicle under acceleration.

Accordingly, there is a need for a rear suspension system for atwo-wheeled motor vehicle, which improves rear wheel geometry. Such asystem should also increase lateral stability of the rear wheel of thevehicle and improve wheel contact with the pavement. Such a systemshould further contain the power under acceleration and not transferforce back to the front of the vehicle. The present invention fulfillsthese needs and provides other related advantages.

SUMMARY OF THE INVENTION

The present invention resides in a rear suspension system fortwo-wheeled motor vehicles. The system of the present invention has theability to keep the same arc from the wheel axle point and thetransmission drive sprocket positions as the suspension moves upwardlyand downwardly, thus plotting a constant path in relation between axespoints. The system can be adjustable for any desired arc pattern.

The system of the present invention generally comprises upper and lowerpivot arm assemblies pivotally connected to the frame of the vehicle. Acontrol arm is interconnected between the pivot arm assemblies. A rearwheel supporting unit, comprised of upper and lower arm assemblies, isconnectable to an axle of a rear wheel of the vehicle at a first endthereof. An upper second end of the supporting unit is connected to theupper pivot arm assembly. A lower end of the rear wheel supporting unitis connected to the lower pivot arm assembly. A compressible shock unitis connected between the rear wheel supporting unit and the vehicleframe. Typically, the compressible shock is connected to either thelower pivot arm assembly, or the rear wheel supporting unit at one endthereof, and the vehicle frame at the opposite end thereof.Alternatively, the shock may be connected to either the upper pivot armassembly and frame, or upper arm assembly and frame.

In a first embodiment, the rear suspension system includes generallyparallel and spaced apart first and second axle plates having alignedapertures for accepting an axle of the rear wheel. The first and secondaxle plates are connected to the first ends of the upper and lower armassemblies.

The upper arm assembly is comprised of a base pivotally connected to theupper pivot arm assembly, and having a first elongated arm extendingfrom the base to the connection point at the first axle plate, and asecond elongated arm extending from the base generally parallel to thefirst arm to a connection point at the second support axle plate. Thelower arm assembly comprises a base connected to the lower pivot armassembly. A first elongated arm extends from the base to a connectionpoint at the first support axle plate. A second elongated arm extendsfrom the base generally parallel to the first arm to a connection pointat the second support axle plate. It will be understood by those skilledin the art that the various connection points may be pivotal, dependingupon the intended characteristics of the system.

In a second embodiment, the lower arm assembly comprises a baseconnected to the lower pivot arm assembly, and has a first elongated armextending from the base and including a connection point for the rearwheel, such as an aperture formed therein. A second elongated armextends from the base generally parallel to the first arm and includes aconnection point, typically an aligned aperture, for the rear wheel. Theupper arm assembly is comprised of a base pivotally connected to theupper pivot arm assembly, and first and second elongated arms whichextend from the base to connection points at the lower arm assembly.Such connection points may be pivotal.

The lower pivot arm assembly comprises a pair of angular brackets whichare spaced apart from one another so as to be generally parallel, andhaving a shaft extending between ends thereof for pivotal connection tothe vehicle frame. A shaft extends through second ends thereof forpivotal connection to the rear wheel support unit, the base or lowerarms of the lower arm assembly.

The control arm and elongated arms of the upper and lower assemblies maybe adjustable in length.

The above-described system has a generally triangular configuration.With the system of the present invention, lateral stability is createdfor the rear wheel of the two-wheeled vehicle. In addition the axlelocation for the wheel is controlled in a structured motion in relationto the drive system, sprocket or shaft. The length of the arm assembliesand the length of the pivot arm assemblies interconnected with thecontrol arms achieve the ability to position the rear axle in aunlimited number of positions in relation to the frame. This also meansthat it has the ability for a maintained equal distance from the drivesystem, sprocket or shaft in relation to the rear axle location inmotion thus allowing no slack to be created in the drive system.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a side elevational view of a motorcycle incorporating a rearsuspension system embodying the present invention;

FIG. 2 is a perspective view of the rear suspension system similar tothat illustrated in FIG. 1;

FIG. 3 is a side elevational view of the rear suspension system of FIG.2 in a relaxed state;

FIG. 4 is a side elevational view of the rear suspension system of FIG.2 in a compressed state;

FIG. 5 is a side elevational view of the rear suspension system showingaltered pivot point and shock locations;

FIG. 6 is a side elevational view of the rear suspension system similarto that illustrated in FIG. 5 displaying an inverted upper pivot armassembly; and

FIG. 7 is a side elevational view of the rear suspension system,illustrating a shock absorber interconnected between the frame and upperportion of the rear suspension system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the drawings for purposes of illustration, the presentinvention is concerned with a rear suspension system for two-wheeledvehicles, generally referred to by the reference number 10 in FIGS. 1-6.The rear suspension system 10 is particularly designed and adapted foruse in a motorcycle 16, although it could conceivably be incorporatedinto any two-wheeled vehicle.

With reference to FIG. 1, a motorcycle 16 is illustrated incorporatingthe rear suspension system 10 of the present invention. The primarystructural component of the motorcycle is the frame 12. The frame 12 istypically comprised of two bottom support tubes 20 which are bent at anupwardly directed angle at a front end thereof to a head tube 22. Thehead tube 22 is connected to a front wheel torque assembly 24 upon whichthe front wheel 26 is rotatably mounted. The bottom support tubes 20also provide an anchor and base for the motor 28, transmission 30, etc.A top support tube 32 extends from the head tube 22 towards the rear ofthe motorcycle 16, and supports the gas tank 34, seat 36, etc. A rearpair of tube 38 interconnects the top and bottom support tubes 32 and20, and serve as a rear end of the overall frame 12. Conventionally, therear suspension is connected to the rear pair of tubes 38 with crossbars or the like. In the present invention, a generally triangulartriaxial suspension system 10 extends between the rear tubes 38 and therear wheel 18 of the motorcycle 16.

With reference to FIG. 2, the rear suspension system 10 of the presentinvention includes an upper pivot arm assembly 134 comprising a pair ofangular brackets 136 and 138 spaced apart and generally parallel to oneanother. A first base 140 extends between the first ends thereof for thepivotal connection between the rear tubes 38 of the frame 12, typicallyby pins 152 and 154 extending between the mounting ears 72 and 74extending from the upper frame unit 68 and 70 extending from the reartubes 38 of the frame 12. Of course, other appropriate means ofpivotally connecting the upper pivot arm assembly 134 to the rearportion of the frame 38 can also be used. A second base 144 extendsbetween the second ends thereof for the pivotal connection between theupper arm assembly arms 62 and 64, typically by pins 156 and 158extending between the upper pivot arm brackets 136 and 138 extending tothe upper arms assembly 54 and 56. Of course, other appropriate means ofpivotally connecting the upper pivot arm assembly 134 to the upper armassembly 50 can also be used. The upper arm assembly 50 is generallyU-shaped, and includes a base 52 having first and second elongated arms54 and 56 extending thereof to connection points 58 and 60 of the axleplates 42 and 44, respectively, which may be pivotal. Typically, thearms 54 and 56 are rigidly connected to an upper portion of the upperarm assembly 52 which allows the arms 54 and 56 to pivot and rotate,such as rocker arm fasteners, pins, bushings, etc. The upper armassembly 50 is pivotally connected to the upper pivot arm assembly 134typically by pins 156 and 158 extending between upper pivot arm brackets136 and 138 extending between the first and second elongated arms 54 and56 from the base shaft 52. Of course, other appropriate means ofpivotally connecting the upper arm assembly 50 to the upper pivot armassembly can also be used.

A lower arm assembly 78 extends adjacent to a lower portion of the rearend 38 of frame 12, and a lower end of each axle plate 42 and 44. Thelower arm assembly 78 includes a general U-shaped member having a base80 and elongated arms 82 and 84 extending from the base 80 to aconnection point on each respective axle plate 42 and 44.

The lower arm assembly 78 is pivotally connected to the frame 12 via alower pivot arm assembly 90. This assembly 90 is generally H-shaped andincludes two brackets, 92 and 94 which are angled and spaced apart fromone another so as to be generally parallel to one another. A shaft orpin 96 extends between a first end of the brackets 92 and 94 for pivotalconnection to mounting ears 98 and 100 extending from the rear frametubes 38. Similarly, a shaft or pin 102 extends through the oppositeends of the brackets 92 and 94 for pivotal connection to lower armassembly 82 and 84, usually intermediate ends thereof. Although thepivot arms 90 and 134 are illustrated as having an angled configuration,it should be understood by the reader that the invention is not limitedto such, the pivot arms also being capable of being designed to bestraight and without angle.

The lower arm assembly 78 may include pivotal connections 188 to axleplates 42 and 44, as shown in FIG. 7, thus allowing the upper armassembly 50 to be solidly connected to the axle plates 42 and 44.

The upper and lower arm assemblies are collectively referred to hereinas a rear wheel supporting unit, which serves to connect to an axle ofthe rear wheel of the vehicle.

The control arm assembly 160 is pivotally interconnected to the upperpivot arm assembly 134 and the lower pivot arm assembly 90. The firstends of control arms 162 and 164 are pivotally connected to the upperpivot arm assembly 134 typically by pins 166 and 168 extending betweenmounting ears 148 and 150 extending from the upper pivot arm plates 136and 138. The second ends of the control arms 162 and 164 are pivotallyconnected to the lower pivot arm assembly 90 between the mounting ears104 and 106, typically by pins 170 and 172, extending from the lowerbrackets 92 and 94. Although two control arms 162 and 164 are shown,only one control arm may be used.

A shock unit 112, such as a shock absorber typically having acompressible spring, is pivotally interconnected between the rear wheelsupporting unit and the frame 12 of the motorcycle 16. As shown in FIGS.2-4, the shock unit 12 is interconnected between the lower tubes 20 ofthe frame 12 and the lower arm assembly 78 or pivot arm assembly 90.Typically, this is done by connecting an upper end of the shock unit 112with an appropriate fastener 118 and 120, such as a rotatable pin or thelike, to mounting ears 114 and 116 extending from the lower tubes 20 ofthe frame 12, or any other rear end portion of the frame 12. Theopposite end of the shock unit 112 is pivotally attached intermediateends of the lower arm assembly brackets 122 and 124. This is done byattaching the appropriate fastener, such as pins 126 and 128 or thelike. The shock, or shock units unit shown in the horizontal positionmay be also placed in the vertically position upwardly within thevertical frame rails 38 and 40 as shown in FIG. 5.

FIG. 3 illustrates the suspension system 10 in a relaxed state. FIG. 4illustrates the suspension system 10 in a compressed state, such as whenthe rear wheel 18 encounters a bump. As the motorcycle 16 moves and issubjected to uneven surface bumps or ruts, the system 10 acts in thefollowing manner. The overall movement can best be described as aknee-action movement. As the shock unit 112 is compressed from upperpressure of the wheel 18, the pivot arm assemblies 94 and 138 arepivoted upwardly about the axis of fasteners. This results in the lowerarm assembly 90 pivoting in an upward planar motion causing the controlarm 164 to release the upper pivot arm assembly 138 to pivot in arelative motion thus controlling the motion of the axle plates 42 and 44to move upwardly in a planar motion as well. The upper arm assembly 50also articulates and pivots upwardly in response. The upwardly directedplanar motion results in controlled directional movement. The amount oftravel of motion of the upward arm is controlled by the shock unit 112.As this pressure is reduced, the system 10 reverses this action andconforms to its balanced pre-shock tension position, as illustrated inFIG. 3. The system 10 maintains tension through the weight of themotorcycle 16 pressing down on the shock unit 112.

The downward rebound pivotal motion of the rear suspension system 10 isessentially the reverse of that described above. As the compressibleshock unit 112 decompresses after rebound, the lower pivot arm assembly94 pivots in a downward motion causing the control arms 164 to pull onthe upper pivot arm assembly 138 to pivot in a relative motion thus thelower arm assembly 84 to move in a downward motion. This in turn causesthe axle support plate 44 to move downward, resulting in the upper armassembly 56 being pulled downward also. The upwardly and downwardlydirected motions are eventually ceased by virtue of the shock-absorbingunit 112.

With reference to FIG. 3 adjustable screw assemblies 174, 176, 178 areshown that may be placed on the arm assemblies 164, 56, 84 and on theopposite ends of the arm assemblies for use of tuning the suspension.These adjustable screw assemblies 174, 176, 178 may motion the armassemblies to a location that may help alignment and control travel thatwill benefit the suspension system stability. The control arm assembly164 displays the adjustable screw assembly 174 which consist of a malescrew unit attached to the control arm assembly 164 and a counter partfemale screw receiver attached to the other end with a locking devicesuch as a jam nut or the like. Additionally the upper arm assembly 56displays a adjustable screw assembly 176 and the lower arm assembly 84displays a adjustable screw assembly 178 which consist of the samedescription as the adjustable screw assembly 174. These adjustable screwassemblies 174, 176, 178 as described may be placed on opposite ends ofthe arm assemblies. Of course, other means of making the control armsand assemblies adjustable which are known in the art are contemplated bythe invention as well.

With reference to FIG. 5, the rear suspension system 10 of the presentinvention is shown with the upper arm assembly 56 pivotally connected 66to the lower arm assembly 84 at a mid-location on the lower arm assembly84. This pivotal connection point 66 may be connected anywhere along thelower arm assembly 84. The shock unit 112 may be located in a upwardconnection to the upper frame area 70 with a pivotal connection point130. Alternatively, the lower part of the shock 112 with a pivotalconnection point 132 to the lower arm assembly 84 or in conjunction or apart of the lower pivot arm assembly 94. The shock unit 112 may also bedirectly pivotally connected to the lower pivot arm assembly 94 in thesame manner. This described embodiment functions in the same manner asdescribed in the reference to FIG. 3 and FIG. 4. The shock 112 islocated in a upwardly location and compresses upwardly and downwardly.

With reference to FIG. 6, the rear suspension system 10 of the presentinvention is shown with the upper pivot arm assembly 142 inverted with apivotal connection 140 to the upper frame ear 74. The opposite end ispivotally connected 64 with pins and fasteners 158 to the upper armassembly 50. Shown also is the same shock 112 mounted configuration asin FIG. 5. The shock unit 112 may be connected to the lower pivot arm 94as in the same manner as described in FIG. 5.

With reference now to FIG. 7, the shock unit 12 may also beinterconnected between upper frame member 34 and the upper arm assembly50 and/or the upper pivot arm assembly 142. The shock unit 112 ispivotally connected to the frame member 34 at connection points 180 and182 at one end thereof. At the opposite end thereof, a pivotalconnection 184 and 186 is made between the arms 56 of the upper armassembly 50. Such can be made with pins and fasteners or the like. Thus,it will be appreciated by those skilled in the art, that the position ofthe shock unit 112 is not necessarily critical, so long as the system 10is free to move as intended and jars and bumps are dampened due to theshock absorber 112.

With reference to FIG. 6, the motion of the rear suspension 10 from therelaxed state starts with the compression of the shock 112. The lowerpivot arm 94 pivots from the frame area 40 from the ears 100 upwardlyfrom the pivotal point 96 to the pivotal connection 172 allowing thecontrol arm 164 to motion upwardly. The pivotable connection 168 in turncontrols the pivot arm 142 to pivot upwardly and forward. The upperpivot arm 142 which is pivotally connected to the frame area 70 from theears 74 from the pivotal connection point 140 motions upwardly andallows the pivotal connection point 158 to motion the upper arm 56 tomotion upwardly also. This allows the lower arm 84 to pivot upwardlyfrom pivot connection point 66 thus allowing the axle connection point48 to move upwardly in addition to the lower pivot arm 94 pivotalconnection point 102 to the lower arm 84 motioning the lower arm 84 tomove back and upwardly thus allowing the wheel 18 to rise and providemotion in the suspension.

The opposite happens as the shock 112 decompresses. The lower pivot arm94 moves downwardly pulling on the control arm 164 from pivotalconnection 172 thus pulling on the upper pivot arm 142 to motion downand rearward from pivotal connection 168. This motion allows the upperarm 56 to motion down via pivotal connection 158 and push the lower arm84 down which is connected to the axle connection point 48 to movedownwardly allowing the wheel 18 to motion downwardly with thesuspension 10.

Use of the present invention is advantageous over existing rearsuspension systems in that improved rear wheeled contact with the groundis achieved. Also, rear wheel control and stability is also greatlyincreased, resulting in additional safety. Improved arc from the rearaxle sprocket location in relation to the transmission sprocket isachieved allowing the ability to provide an exact arc that does notallow slack in the drive system (chain belt etc.), thus allowing drivesystems on suspension units that otherwise would not be possible.

The placement of the upright frame rear frame rails 38 and 40 may alsobe placed inboard on the rear frame platform between 34 and 20 to allowdrive systems to be placed on the outside of these rails. The upper andlower arms that extend out to the axle support plate then can be routedaround the drive system.

Although several embodiments have been described in detail for purposesof illustration, various modifications may be made to each withoutdeparting from the scope and spirit of the invention. Accordingly, theinvention is not to be limited, except as by the appended claims.

Accordingly, there is a continuing need for a [insert invention title]so as to overcome the aforementioned disadvantages. The presentinvention fulfills this need and provides other related advantages.

1. A rear suspension system for a motorcycle, comprising: an upper pivotarm assembly pivotally connected to a frame of the vehicle; a lowerpivot arm assembly pivotally connected to the frame of the vehicle; acontrol arm having a first end thereof connected to the upper pivot armassembly, and a generally opposite second end thereof connected to thelower pivot arm assembly; means for supporting an axle of a rear wheelof the motorcycle; a rear wheel support unit pivotally connected to therear wheel axle support means at a first end thereof, and having anupper second end thereof connected to the upper pivot arm assembly, andhaving a lower second end thereof connected to the lower pivot armassembly; and a compressible shock unit interconnected between the rearwheel support unit at one end thereof, and the vehicle frame at theopposite end thereof.
 2. The system of claim 1, wherein the axle supportmeans comprise first and second spaced apart and parallel support axleplates having aligned apertures configured to receive the axle of therear wheel.
 3. The system of claim 2, wherein the rear wheel supportunit comprises an upper arm assembly pivotally connected to the firstand second axle plates and extending to the upper pivot arm assembly,and a lower arm assembly connected to the first and second axle platesand extending to the lower pivot arm assembly.
 4. The system of claim 3,wherein the upper arm assembly is pivotally connected to the upper pivotarm assembly.
 5. The system of claim 3, wherein the upper arm assemblycomprises a first elongated arm extending from a pivotal connection withthe first axle plate to the upper pivot arm assembly, and a secondelongated arm extending from a pivotal connection with the second axleplate to the upper pivot arm assembly and generally parallel to thefirst arm.
 6. The system of claim 5, including a base extending betweenthe first and second arms of the upper arm assembly.
 7. The system ofclaim 5, wherein the first and second arms of the upper arm assembly arepivotally connected to the upper pivot arm assembly.
 8. The system ofclaim 3, wherein the lower arm assembly is pivotally connected to thelower pivot arm assembly.
 9. The system of claim 1, wherein the rearwheel supporting unit comprises an upper arm assembly connected to thefirst and second axle plates and extending to the upper pivot armassembly, and a lower arm assembly pivotally connected to the first andsecond axle plates and extending to the lower pivot arm assembly. 10.The system of claim 9, wherein the lower arm assembly is pivotallyconnected to the lower pivot arm assembly.
 11. The system of claim 9,wherein the lower arm assembly comprises a first elongated arm extendingfrom a pivotal connection with the first axle plate to the lower pivotarm assembly, and a second elongated arm extending from a pivotalconnection with the second axle plate to the lower pivot arm assemblyand generally parallel to the first arm.
 12. The system of claim 11,including a base extending between the first and second arms of thelower arm assembly.
 13. The system of claim 11, wherein the first andsecond arms of the lower arm assembly are pivotally connected to thelower pivot arm assembly.
 14. The system of claim 9, wherein the upperarm assembly is pivotally connected to the upper pivot arm assembly. 15.The system of claim 1, wherein the lower pivot arm assembly comprises apair of angular brackets spaced apart and generally parallel to oneanother and having a shaft extending between first ends thereof forpivotal connection to the vehicle frame, and a shaft extending throughsecond ends thereof for pivotal connection to the rear wheel supportunit.
 16. The system of claim 3, wherein the shock unit is pivotallyconnected to the vehicle frame at an end of the shock unit generallyopposite the lower arm assembly.
 17. A rear suspension system fortwo-wheeled vehicles, comprising: first and second spaced apart andparallel support axle plates having aligned apertures configured toreceive an axle of a rear wheel of the two-wheeled vehicle; an upperpivot arm assembly pivotally connected to a frame of the vehicle; anupper arm assembly pivotally connected to the upper pivot arm assemblyand extending to a pivotal connection to the first and second axleplates, the upper arm assembly including a first elongated arm and asecond elongated arm generally parallel to the first arm; a lower pivotarm assembly pivotally connected to the vehicle frame; a lower armassembly pivotally connected to the lower pivot arm assembly andextending to the first and second axle plates, the lower arm assemblyincluding a first elongated arm and a second elongated arm generallyparallel to the first arm; a control arm having a first end thereofconnected to the upper pivot arm assembly, and a generally oppositesecond end thereof connected to the lower pivot arm assembly; and acompressible shock unit connected at a first end thereof to the frameand extending to either the upper or lower arm assembly or upper orlower pivot arm assembly at the opposite second end thereof.
 18. Thesystem of claim 17, wherein the shock unit is pivotally connected to thevehicle frame at the first end thereof, and pivotally connected toeither the upper or lower arm assembly or upper or lower pivot armassembly at the second end thereof.
 19. The system of claim 17, whereinthe first elongated arm of the upper arm assembly extends from a pivotalconnection with the first axle plate to the upper pivot arm assembly,and the second elongated arm extends generally parallel to the first armfrom a pivotal connection with the second axle plate to the upper pivotarm assembly.
 20. The system of claim 19, including a base extendingbetween the first and second arms of the upper arm assembly.
 21. A rearsuspension system for two-wheeled vehicles, comprising: first and secondspaced apart and parallel support axle plates having aligned aperturesconfigured to receive an axle of a rear wheel of the two-wheeledvehicle; an upper pivot arm assembly pivotally connected to a frame ofthe vehicle; an upper arm assembly pivotally connected to the upperpivot arm assembly and extending to a connection to the first and secondaxle plates, the upper arm assembly including a first elongated arm anda second elongated arm generally parallel to the first arm; a lowerpivot arm assembly pivotally connected to the vehicle frame; a lower armassembly pivotally connected to the lower pivot arm assembly andextending to a pivotal connection with the first and second axle plates,the lower arm assembly including a first elongated arm and a secondelongated arm generally parallel to the first arm; a control arm havinga first end thereof connected to the upper pivot arm assembly, and agenerally opposite second end thereof connected to the lower pivot armassembly; and a compressible shock unit connected at a first end thereofto the frame and extending to either the upper or lower arm assembly orupper or lower pivot arm assembly at the opposite second end thereof.22. The system of claim 21, wherein the shock unit is pivotallyconnected to the vehicle frame at the first end thereof, and pivotallyconnected to either the upper or lower arm assembly or upper or lowerpivot arm assembly at the second end thereof.
 23. The system of claim21, wherein the first elongated arm of the lower arm assembly extendsfrom a pivotal connection with the first axle plate to the lower pivotarm assembly, and the second elongated arm extends generally parallel tothe first arm from a pivotal connection with the second axle plate tothe lower pivot arm assembly.
 24. The system of claim 23, including abase extending between the first and second arms of the lower armassembly.